Ih contributes to synchronized AP firing in response to small depolarizing currents. (A) Representative APs measured from the same WT SGN (P4, apex) before (black traces) and after treatment with 100 µM ZD7288 (red traces). For each condition, a series of 20 APs were evoked using threshold current steps. Note the delay and larger distribution in spike latency after application of ZD7288. (B) Representative averaged (P4, apex) spike waveforms before (black trace) and after ZD7288 (red trace). Spikes were aligned with their peaks at time 0 and averaged. (C) Scatter plot showing spike latency for three different current injections from the same 12 cells (P1–4) before (black symbols) and after treatment with 100 µM ZD7288 (red symbols). The mean latency is indicated by horizontal lines (**, P < 0.01). Note the variation in spike latency is significantly increased for small depolarizing current steps (30 and 40 pA) in the presence of 100 µM ZD7288 but is minimal for larger steps (≥50 pA). CI (95%) of mean difference was used to quantify the degree of variation in spike latency before and after treatment with ZD7288. 30 pA: 1.55 < CI 95% < 6.83 ms; 40 pA: 0.93 < CI 95% < 3.18 ms; 50 pA: 0.28 < CI 95% < 1.70 ms.
